1. Field of the Invention
The present invention relates to a semiconductor structure.
2. Description of the Related Art
For current integrated circuit processing, controllers, memories, low-voltage (LV) circuits and high-voltage (HV) power devices are integrated into a single chip, referred to as a single-chip system. For example, to handle high voltage and current, double-diffused metal oxide semiconductor (DMOS) transistors, frequently used as conventional power devices, can operate with low on-resistance while sustaining high voltage. Lateral double-diffused metal oxide semiconductor (LDMOS) transistors in particular have a simple structure suitable for incorporation into VLSI logic circuits.
However, the surface field of a lateral double-diffused metal oxide semiconductor limits the voltage tolerance of transistors therein. Moreover, when operating an LDMOS device of an interdigitated structure, a high electric field occurring adjacent to the tip of the finger-shaped source results in decreased breakdown voltage of the device. Particularly, a higher electric field, caused from a smaller device size as well as smaller width of the source or smaller curvature radius of the finger end, results in a very serious decrease of breakdown voltage. However, if the width of the finger shaped source is widened to enlarge the curvature radius of the finger end in order to increase the breakdown voltage and eliminate the problem mentioned above, layout flexibility of the device is sacrificed, thus hindering development for further scaling-down of related devices.
An improved semiconductor device ameliorating the disadvantages of the conventional technology is desirable.